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.Dd $Mdocdate: September 21 2020 $
.Dt SSL 3
.Os
.Sh NAME
.Nm ssl
.Nd OpenSSL SSL/TLS library
.Sh DESCRIPTION
The OpenSSL
.Nm ssl
library implements the Transport Layer Security (TLS v1) protocols.
.Pp
An
.Vt SSL_CTX
object is created as a framework to establish TLS/SSL enabled connections (see
.Xr SSL_CTX_new 3 ) .
Various options regarding certificates, algorithms, etc., can be set in this
object.
.Pp
When a network connection has been created, it can be assigned to an
.Vt SSL
object.
After the
.Vt SSL
object has been created using
.Xr SSL_new 3 ,
.Xr SSL_set_fd 3
or
.Xr SSL_set_bio 3
can be used to associate the network connection with the object.
.Pp
Then the TLS/SSL handshake is performed using
.Xr SSL_accept 3
or
.Xr SSL_connect 3
respectively.
.Xr SSL_read 3
and
.Xr SSL_write 3
are used to read and write data on the TLS/SSL connection.
.Xr SSL_shutdown 3
can be used to shut down the TLS/SSL connection.
.Sh DATA STRUCTURES
Currently the OpenSSL
.Nm ssl
library functions deal with the following data structures:
.Bl -tag -width Ds
.It Vt SSL_METHOD No (SSL Method)
That's a dispatch structure describing the internal
.Nm ssl
library methods/functions which implement the various protocol versions.
It's needed to create an
.Vt SSL_CTX .
See
.Xr TLS_method 3
for constructors.
.It Vt SSL_CIPHER No (SSL Cipher)
This structure holds the algorithm information for a particular cipher which
is a core part of the SSL/TLS protocol.
The available ciphers are configured on an
.Vt SSL_CTX
basis and the actually used ones are then part of the
.Vt SSL_SESSION .
.It Vt SSL_CTX No (SSL Context)
That's the global context structure which is created by a server or client
once per program lifetime and which holds mainly default values for the
.Vt SSL
structures which are later created for the connections.
.It Vt SSL_SESSION No (SSL Session)
This is a structure containing the current TLS/SSL session details for a
connection:
.Vt SSL_CIPHER Ns s ,
client and server certificates, keys, etc.
.It Vt SSL No (SSL Connection)
That's the main SSL/TLS structure which is created by a server or client per
established connection.
This actually is the core structure in the SSL API.
At run-time the application usually deals with this structure which has
links to mostly all other structures.
.El
.Sh HEADER FILES
Currently the OpenSSL
.Nm ssl
library provides the following C header files containing the prototypes for the
data structures and functions:
.Bl -tag -width Ds
.It Pa ssl.h
That's the common header file for the SSL/TLS API.
Include it into your program to make the API of the
.Nm ssl
library available.
It internally includes both more private SSL headers and headers from the
.Em crypto
library.
Whenever you need hardcore details on the internals of the SSL API, look inside
this header file.
.It Pa ssl2.h
That's the sub header file dealing with the SSLv2 protocol only.
.Bf Em
 Usually you don't have to include it explicitly because it's already included
by
.Pa ssl.h .
.Ef
.It Pa ssl3.h
That's the sub header file dealing with the SSLv3 protocol only.
.Bf Em
Usually you don't have to include it explicitly because it's already included
by
.Pa ssl.h .
.Ef
.It Pa ssl23.h
That's the sub header file dealing with the combined use of the SSLv2 and SSLv3
protocols.
.Bf Em
Usually you don't have to include it explicitly because it's already included
by
.Pa ssl.h .
.Ef
.It Pa tls1.h
That's the sub header file dealing with the TLSv1 protocol only.
.Bf Em
Usually you don't have to include it explicitly because it's already included
by
.Pa ssl.h .
.Ef
.El
.Sh API FUNCTIONS
.Ss Ciphers
The following pages describe functions acting on
.Vt SSL_CIPHER
objects:
.Xr SSL_get_ciphers 3 ,
.Xr SSL_get_current_cipher 3 ,
.Xr SSL_CIPHER_get_name 3
.Ss Protocol contexts
The following pages describe functions acting on
.Vt SSL_CTX
objects.
.Pp
Constructors and destructors:
.Xr SSL_CTX_new 3 ,
.Xr SSL_CTX_set_ssl_version 3 ,
.Xr SSL_CTX_free 3
.Pp
Certificate configuration:
.Xr SSL_CTX_add_extra_chain_cert 3 ,
.Xr SSL_CTX_get0_certificate 3 ,
.Xr SSL_CTX_load_verify_locations 3 ,
.Xr SSL_CTX_set_cert_store 3 ,
.Xr SSL_CTX_set_cert_verify_callback 3 ,
.Xr SSL_CTX_set_client_cert_cb 3 ,
.Xr SSL_CTX_set_default_passwd_cb 3 ,
.Xr SSL_CTX_set_tlsext_status_cb 3
.Pp
Session configuration:
.Xr SSL_CTX_add_session 3 ,
.Xr SSL_CTX_flush_sessions 3 ,
.Xr SSL_CTX_sess_number 3 ,
.Xr SSL_CTX_sess_set_cache_size 3 ,
.Xr SSL_CTX_sess_set_get_cb 3 ,
.Xr SSL_CTX_sessions 3 ,
.Xr SSL_CTX_set_session_cache_mode 3 ,
.Xr SSL_CTX_set_timeout 3 ,
.Xr SSL_CTX_set_tlsext_ticket_key_cb 3
.Pp
Various configuration:
.Xr SSL_CTX_get_ex_new_index 3 ,
.Xr SSL_CTX_set_tlsext_servername_callback 3
.Ss Common configuration of contexts and connections
The functions on the following pages each come in two variants:
one to directly configure a single
.Vt SSL
connection and another to be called on an
.Vt SSL_CTX
object, to set up defaults for all future
.Vt SSL
connections created from that context.
.Pp
Protocol and algorithm configuration:
.Xr SSL_CTX_set_alpn_select_cb 3 ,
.Xr SSL_CTX_set_cipher_list 3 ,
.Xr SSL_CTX_set_min_proto_version 3 ,
.Xr SSL_CTX_set_options 3 ,
.Xr SSL_CTX_set_tlsext_use_srtp 3 ,
.Xr SSL_CTX_set_tmp_dh_callback 3 ,
.Xr SSL_CTX_set1_groups 3
.Pp
Certificate configuration:
.Xr SSL_CTX_add1_chain_cert 3 ,
.Xr SSL_CTX_get_verify_mode 3 ,
.Xr SSL_CTX_set_client_CA_list 3 ,
.Xr SSL_CTX_set_max_cert_list 3 ,
.Xr SSL_CTX_set_verify 3 ,
.Xr SSL_CTX_use_certificate 3 ,
.Xr SSL_get_client_CA_list 3
.Xr SSL_set1_param 3
.Pp
Session configuration:
.Xr SSL_CTX_set_generate_session_id 3 ,
.Xr SSL_CTX_set_session_id_context 3
.Pp
Various configuration:
.Xr SSL_CTX_ctrl 3 ,
.Xr SSL_CTX_set_info_callback 3 ,
.Xr SSL_CTX_set_mode 3 ,
.Xr SSL_CTX_set_msg_callback 3 ,
.Xr SSL_CTX_set_quiet_shutdown 3 ,
.Xr SSL_CTX_set_read_ahead 3 ,
.Xr SSL_set_max_send_fragment 3
.Ss Sessions
The following pages describe functions acting on
.Vt SSL_SESSION
objects.
.Pp
Constructors and destructors:
.Xr SSL_SESSION_new 3 ,
.Xr SSL_SESSION_free 3
.Pp
Accessors:
.Xr SSL_SESSION_get_compress_id 3 ,
.Xr SSL_SESSION_get_ex_new_index 3 ,
.Xr SSL_SESSION_get_id 3 ,
.Xr SSL_SESSION_get_protocol_version 3 ,
.Xr SSL_SESSION_get_time 3 ,
.Xr SSL_SESSION_get0_peer 3 ,
.Xr SSL_SESSION_has_ticket 3 ,
.Xr SSL_SESSION_set1_id_context 3
.Pp
Encoding and decoding:
.Xr d2i_SSL_SESSION 3 ,
.Xr PEM_read_SSL_SESSION 3 ,
.Xr SSL_SESSION_print 3
.Ss Connections
The following pages describe functions acting on
.Vt SSL
connection objects:
.Pp
Constructors and destructors:
.Xr SSL_new 3 ,
.Xr SSL_dup 3 ,
.Xr SSL_free 3 ,
.Xr BIO_f_ssl 3
.Pp
To change the configuration:
.Xr SSL_clear 3 ,
.Xr SSL_set_SSL_CTX 3 ,
.Xr SSL_copy_session_id 3 ,
.Xr SSL_set_bio 3 ,
.Xr SSL_set_connect_state 3 ,
.Xr SSL_set_fd 3 ,
.Xr SSL_set_session 3 ,
.Xr SSL_set1_host 3 ,
.Xr SSL_set_verify_result 3
.Pp
To inspect the configuration:
.Xr SSL_get_certificate 3 ,
.Xr SSL_get_default_timeout 3 ,
.Xr SSL_get_ex_new_index 3 ,
.Xr SSL_get_fd 3 ,
.Xr SSL_get_rbio 3 ,
.Xr SSL_get_SSL_CTX 3
.Pp
To transmit data:
.Xr DTLSv1_listen 3 ,
.Xr SSL_accept 3 ,
.Xr SSL_connect 3 ,
.Xr SSL_do_handshake 3 ,
.Xr SSL_read 3 ,
.\" XXX enable after the 6.8 release: Xr SSL_read_early_data 3 ,
.Xr SSL_renegotiate 3 ,
.Xr SSL_shutdown 3 ,
.Xr SSL_write 3
.Pp
To inspect the state after a connection is established:
.Xr SSL_export_keying_material 3 ,
.Xr SSL_get_client_random 3 ,
.Xr SSL_get_ex_data_X509_STORE_CTX_idx 3 ,
.Xr SSL_get_peer_cert_chain 3 ,
.Xr SSL_get_peer_certificate 3 ,
.Xr SSL_get_server_tmp_key 3 ,
.Xr SSL_get_servername 3 ,
.Xr SSL_get_session 3 ,
.Xr SSL_get_shared_ciphers 3 ,
.Xr SSL_get_verify_result 3 ,
.Xr SSL_get_version 3 ,
.Xr SSL_session_reused 3
.Pp
To inspect the state during ongoing communication:
.Xr SSL_get_error 3 ,
.Xr SSL_get_shutdown 3 ,
.Xr SSL_get_state 3 ,
.Xr SSL_num_renegotiations 3 ,
.Xr SSL_pending 3 ,
.Xr SSL_rstate_string 3 ,
.Xr SSL_state_string 3 ,
.Xr SSL_want 3
.Ss Utility functions
.Xr SSL_alert_type_string 3 ,
.Xr SSL_dup_CA_list 3 ,
.Xr SSL_load_client_CA_file 3
.Ss Obsolete functions
.Xr OPENSSL_init_ssl 3 ,
.Xr SSL_COMP_add_compression_method 3 ,
.Xr SSL_CTX_set_tmp_rsa_callback 3 ,
.Xr SSL_library_init 3 ,
.Xr SSL_set_tmp_ecdh 3
.Sh SEE ALSO
.Xr openssl 1 ,
.Xr crypto 3 ,
.Xr tls_init 3
.Sh HISTORY
The
.Nm
document appeared in OpenSSL 0.9.2.
